Tuesday, 23 October 2012

3G/4G antennas for boating and waterways

We often get asked about antenna solutions to enable 3G broadband for boats used on rivers and waterways. Due to the very nature of the application, fixed line access is just not possible unless the vessel is moored up in one place permanently. Therefore using mobile or wireless broadband makes perfect sense for users who need high speed internet on the move.

From an antenna perspective, there are some challenges especially when the nearest 3G base station may be in a different direction every day/night and where signal strengths and network availability may not be all they might. Therefore antennas that radiate in every direction (known as omni-directional antennas) are most appropriate.

So here is our take on three useful high-gain 3G/4G antenna options for waterways applications:

The first option is a high gain low profile magnetic mount antenna. It requires a reasonable-sized metal surface on which to mount, but supplied with typically 4M of cable which can be routed below deck, it can be flexible enough to provide a significant performance improvement over the antenna built-in to the dongle. With an optimum groundplane, peak gain before cable loss can be up to 4-5 dBi. An example of such antennas can be found here.

A low profile omni antenna is the second option. Whilst not offering as much gain as the magnetic antenna above, it can sit pretty much flush to the deck or roof of the boat. With a 2.5M cable and 3 dBi gain, the low profile can help "move" the signal to enable a dongle to be used inside the boat or below deck. The low profile antenna can be stud-mount or tape-mount. Examples can be found here and here.

The high gain omni-directional antenna option is a more traditional type antenna offering 4-5 dBi gain across the bands. A neat technique is to mount the bracket permanently somewhere on the boat (as high up as possible) and the antenna can be fitted and removed in a matter of seconds so if you are going to have height clearance issues on your travels then this will not cause to much hassle. To go with a high gain omni you would typically need some low loss cable to reduce losses down the cable run, but cables could be run up to 10M if required. An example of the antenna can be found here. A 5M compatible jumper cable looks like this.

In conjunction with these antennas, the correct connector for your 3G device is required. Typically, the following dongle and modem/router manufacturers lean towards the following connectors, though it is worth verifying before you purchase:

Huawei - Common connector CRC9 - CRC Adapters can be found here.
Sierra Wireless - Common connector TS9 - TS9 Adapters can be found here.
Option - Common connector MC-Card - MC-Card Adpaters can be found here.

Often 3G routers will have a SMA-Female Jack for the antenna port. A SMA-Female Jack looks like this:

That means that the antenna will require a SMA-Male connector. The SMA-Male plug looks like this:

For any questions, please feel free to contact us via our websites:


Tuesday, 16 October 2012

Dongle frustration - why 3G dongles and modems need antenna connectors!

The vendors of 3G dongles are consistently missing the point. What's the use in bringing out a 3G dongle that doesn't have a connector for an external antenna i.e. so a high gain antenna can be reliably connected to the dongle?

Given that many 3G dongle/modem users are using cellular networks to access the internet because the leased line infrastructure can't support broadband, this often coincides with being on the fringes of the 3G network as well. In these cases, high gain 3G antennas provide the answer to overcoming weak signal enabling a stable and functional 3G connection for many users. The frustration comes when dongle vendors decide that they don't need to build-in an antenna connector - this makes connecting external antennas quite tricky.

An antenna coupler is often offered as a solution for dongles without antenna connectors, but while this type of solution can work, it can be unreliable and the coupler in itself will introduce losses and attenuation that can be ill-afforded by the dongle user.

It makes sense for users to insist on dongles/modems with 3G antenna connectors - the leading dongle suppliers do have models that use them, for example Huawei typically uses CRC9, Sierra Wireless TS9 and Option use MC connectors. If everybody starts insisting on models with antenna connectors, then it hopefully would make a lasting impression on the vendors.

We can only hope that when it comes to 4G/LTE modems and dongles, the vendors take a more enlightened approach moving forward especially for those customers in locations where network signal strength issues might pose a problem.

For high gain antennas for 3G dongles, visit www.connextech.co.uk

Thursday, 4 October 2012

New 169 MHz Wall-Mount Omni Antenna from EAD

Embedded Antenna Design Ltd (EAD) has today introduced the WMO-169, a new cost-effective and durable VHF antenna designed for wireless metering and related applications at the new 169 MHz EU harmonized frequency band.

 169 MHz Wall Mount Omni Antenna - WMO-169

The WMO-169 is a 169 MHz fibreglass omni antenna mounted onto a compact L-bracket for wall-mounting. Approximately 480mm in length, the antenna is terminated in a N-Female connector and is mounted securely onto the bracket and the bracket is affixed to the wall. The VSWR of the antenna at 169 MHz is better than 1.2:1 and offers 2 dBi gain at centre frequency.

The WCO-169 should be a fed by a jumper cable which can be customised to the appropriate length. Please contact EAD for jumper cable options.

169 MHz ISM band antennas - a reality check!

The introduction of the EU harmonized ISM band at 169 MHz offers utility businesses a viable alternative to higher frequencies for wireless metering. Using the 169 MHz VHF frequency band, wireless metering can be deployed for longer range applications at relatively low power. This has many advantages for operations and billing organisations.

The challenge however comes with specifying 169 MHz antennas to go with the wireless meters. There are already a number of ISM-band 169 MHz module vendors with released products on the market and I am sure there are many more in development. From a RF perspective the module is relatively straightforward, but to supply compact, discrete antennas is not as easy.

A wavelength at 169 MHz is approximately 1.8M in length and therein lies the problem, for even a 1/4 wave monopole would be half a metre in length once the antenna had been housed in a sheath and connectorized.

For metering applications in domestic environments, discrete, tamperproof antennas are desirable, but not only is making a very low profile 169 MHz hard to achieve, it would also need a large groundplane. This is not particularly achievable on a small-sized utility meter. The options really are to use 1/4 wave 169 MHz helical antenna either bulkhead mount with a RF connector or through-hole mount so the antenna cannot be unscrewed from the meter. Both options would be approximately 120mm in overall length and would ideally need a minimum groundplane size of 85mm x 85mm. This size of groundplane could be possible on most meters, but a larger groundplane required by lower profile antennas are just not going to be possible.

Here are two images of the 169 MHz Helical with SMA and the 169 MHz through-hole mount:

169 MHz helical with SMA-Male connector
169 MHz permanent mount with N-Female connector

For concentrator applications (where a number of remote meters communicate with a hub using VHF communications), a wall-mount 169 MHz antenna might come in useful. Designed for outdoor use, ideally these will be of fibreglass construcion to withstand the elements. Here below is an image of the 169 MHz wall-mount antenna:

 169 MHz fibreglass wall-mount omni with bracket

It is also important to be wary of very small 169 MHz antennas as invariably some parameter will be compromised, for example small 169 MHz PCB antennas with a gain of -17.6 dB. It is useful to remember that the laws of physics are not going to change and that the wavelength is always going to be 1.8M. Very small antennas are going to massively compromise RF performance, defeating the very object of the exercise.

In conclusion, the 169 MHz band is a real opportunity for wireless metering and related applications, however the antenna selection and design-in for the meter must be considered early and with the appropriate level of planning to ensure that a suitable antenna design can be accommodated by the meter in terms of available groundplane etc. without comprising performance or aesthetics.

Related links:

An offering of 169 MHz antennas can be found here: